img_file = 'D:\\image\\test.jpg'
    # uuid生成文件名
    key = shortuuid.ShortUUID().random(length=9)
    if img_file.size > 2097152:
      raise exceptions.APIException('图片大小超出限制')
    # file_postfix = img_file.name.split('.')[1]
    suffix = img_file.name.rfind('.')
    if suffix == -1:
      raise exceptions.APIException('图片不正确')
    file_postfix = img_file.name[suffix + 1:] 
    if file_postfix not in ['jpg', 'png', 'gif', 'bmp', 'jpeg', 'JPG', 'PNG',
                'BMP', 'JPEG', ]:
      raise exceptions.APIException('图片格式不正确')
    file_name = key + '.' + file_postfix

 a = '123456'  
 print('下标', a.rfind('5')) 

 a = '123456'  
 print('下标', a.rfind('7'))